What it means
The motor electronics coolant temperature sensor B reports a range/performance condition. Power electronics cooling cannot be regulated reliably.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Motor electronics coolant temperature sensor B reports coolant temperature to the control module so it can manage cooling for the power electronics. P2BD9 sets when Sensor B’s reading is electrically plausible but falls outside the expected range or fails to respond as expected under the observed conditions.
Common causes
Most likely first.
- Sensor characteristic drifted
- Sensor mounting displaced
- Sensor element aged beyond calibration window
Symptoms
- Hybrid-system warning light or message
- Reduced power
- Power electronics overheating warning
How to diagnose it
- Review freeze-frame data and related codes to see Sensor B’s reported temperature and the operating conditions when its range/performance fault set.
- After a cold soak, compare Sensor B’s scan-tool reading with ambient conditions and other available coolant temperature readings for an offset.
- Inspect Sensor B’s mounting and coolant contact using the manufacturer's service information, since a displaced sensor may not track coolant temperature correctly.
- Check Sensor B’s connector and harness for looseness, corrosion, or damage that could distort the reading without creating a clear circuit failure.
- If mounting and wiring are sound, test Sensor B’s response as coolant temperature changes against the manufacturer's specification.
Common fixes
- Reposition and secure Sensor B so it measures coolant as intended.
- Repair a poor connection or damaged wiring affecting Sensor B’s signal.
- Replace Sensor B if its temperature response is outside the manufacturer's specification.
Can I keep driving?
If the vehicle reports power electronics overheating or reduces power, stop safely and avoid continued driving because the cooling system may be controlled from an inaccurate temperature reading. Otherwise, limit driving and arrange diagnosis soon, watching for new warnings.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.